I know that when sub flooring with OSB that it is sugested that you leave an expansion gap of 1/8 inch. Do any of you do this for sub roofing. I would guess not ....but would like to know the practice.

Bonus

12-18-2006 05:37 PM

If you're using "h-clips" then this will do that for you, if not, I put a 2' nail between the sheets for expansion. Actually it has more to do with contraction of the rafter/joist, the OSB is pretty stable.

pmaru77

12-18-2006 05:43 PM

I just did a 9x12 shed and all my seams are on rafters...no gap. So the contraction of the joist brings the OSB onto a collision course? So say the rafter shrinks to 1 7/16 from 1 9/16....so a 1/8 inch collision. But not until many years?

North Country

12-18-2006 10:33 PM

The reason for this 1/8" gap is to take into account the expansive properties of OSB. LEave a sheet out in the rain and you'll see what I mean.

caseywa

12-18-2006 11:21 PM

I had built a roof over our front porch using OSB and did not leave an expansion gap...what a mistake! Over time it was easy to see the bowing that occurred. We had the house reroofed this year by a roofing company with me replacing the the porch roof sheathing.

I wanted to do the work for a couple of reasons...the main one being having access to run some telephone and computer cables to other rooms in the house and to use 3/4 inch ply instead of 1/2 inch the roofing company wanted to use.

An expansion gap of 1/8 inch was used and the areas I felt were too tight I ran the skillsaw along the seam with the blade set at 3/4 inch. The roofing company and building inspector were both pleased with the gaping between the sheets.